Bracing means for canopy doors



April 22, 1941. D. H. MORGAN 2,239,462

BRAGING MEANS FOR oANorY moons April 22, 1941- D. H. MoRGAN BRCING MEANS FOR CANOPY DOORS Filed Jan. 5, 1940 7 a s w w md f www L W u H y 3. @if m 0 W April 22, 1941. D. H. MORGAN BRACING MEANS FOR CANOPY DOORS Filed Jan. 5, 1940 6 Sheets-Sheet 3 W m, s md n, Nm MW MW Nm/f M -O WO/m D @L 3 W m f w mw 4. w ,f

April 22, 1941 D. H. MORGAN 2,239,462

BRACING MEANS FOR CANOFY DOORS Filed Jan. 5, 1940 6 Sheets-Sheet 4 April 22, 1941.

D. H. MoRGArfa BRAGING MEANS FOR CANOPY DOORS Filed Jan. 5, 1940 6 Sheets-Sheet 5 April 22, 1941 D. H. MORGAN 2,239,462

BRACING MEANS FOR CANOPY DOORS Filed Jan. 5, 1940 6 Sheets-Sheet 6 which is disposed therebeneath in raised or open Patented Apr. 22, 1941 BRACING MEANS FOR CANOPY DOORS David H. Morgan, Youngstown, Ohio, assignor to Truscon Steel Compan corporation of Michigan y, Youngstown, Ohio, a

Application January 5, 1940, Serial No. 312,623

8 Claims.

This invention relates to doors, and has particular reference to improvements in so-called a canopy doors; that is to say, doors of the type which, when open, extend horizontally, or substantially horizontally, forwardly, canopy-like, from a doorway at or near the top thereof.

Such doors commonly are used for controlling large doorways, such as the doorways of aircraft hangers, warehouses and the like, and usually they are quite high, wide and heavy, often being com- 1 posedof two or more independent sections disposed in side to side relationship.

Preferably such doors, or door sections, are composed of upper and lower leaves, the lower leaf of which is mounted on the upper leaf to i slide vertically relative thereto to open and close the lower part of the doorway when the upper leaf is disposed vertically closing the upper part of the doorway, and the upper leaf of which is pivoted for swinging movement between a vertically disposed, closed position and a substantially horizontally disposed, open position in which it extends forwardlyfrom the doorway at the top thereof and carries with it the lower leaf position with respect thereto. Thereby, the space in front of the door, for a considerable height and immediately adjacent to the door, may advantageously be utilized for any desired purpose Without interferinglwith operation of the door to open and close either the lower part of the doorway or the complete doorway.

Being, usually, of considerable area, it is important to brace such doors against inward or outward movement due to wind pressure thereagainst or to other causes, especially when the upper leaf is disposed vertically and the lower leaf either is in its lowered, closed position or is being moved to or from open or closed position or is in its raised, open position with respect to said upper leaf. At the same time it is important that such doors be braced by means which do not interfere with utilization of the space behind and adjacent to the door for storage or other purposes.

Accordingly, one special and important object of the present invention is to provide bracing means for doors of the type mentioned which bracing means is disposed so that it does not interfere with utilization of the space behind and adjacent to the door and for a considerable height for storage or other purposes, and which serves eifectively to brace the upper door leaf against swinging movement as long as said upper leaf is disposed vertically closing the upper part of the doorway. 'Ihereby the lower leaf, which can partake only of vertical sliding movement relative to the upper leaf, also is effectively braced against inward or outward movement as long as the upper leaf is disposed vertically and regardless of the closed or open, or partly open, position Vof the lower leaf relative to the upper leaf.

In connection with such doors it is desirable to provide operating means therefor which will operate smoothly and continuously first to raise the lower leaf relative to the upper leaf and then to swing the two leaves as a unit to canopylike position when it is desired to open the entire doorway.V

Accordingly, another special and important object of the present invention is to provide simple, practical means whereby raising of the lower leaf relative to the upper leaf releases the bracing means for the upper leaf to permit the two leaves to be swung as a unit to open position, onlyl however when the lower leaf has reached nearly fully raised or open position relative to the upper leaf, whereby both leaves remain effectively braced when the lower leaf is operated between lowered and nearly fully raised position to open and close the lower part of the doorway.

With the foregoing and other objects in view, which will become more fully apparent as the nature of the invention is better understood, the same consists in the novel features of construction, combination and arrangement of parts as will be hereinafter more fully described, illustrated in the accompanying drawings and defined in the appended claims.

In the accompanying drawings, wherein like characters of reference denote corresponding parts in related views:

Figure 1 is a vertical, transverse section through a canopy door equipped with bracing means constructed and arranged in accordance with one practical embodiment of the invention.

Figure 2 is a diagrammatic perspective view of one practical form of operating means for the door.

Figure 3 is :a section on the line 3--3 of Fig. 1.

Figure 4 is an enlarged view, similar to Fig. l, of the upper part of the door, showing the lower leaf raised to a position in which it is effective by further raising movement to release the door bracing means.

Figure 5 is a View similar to Fig. 4 showing in full lines, the lower leaf raised to a position in which it has' released the door bracing means Figure '7 is a top plan view of the door bracing 5 and operating means.

Figure 8 is a section on the line 8-8 of Fig. 4`

Figure 9 is an enlarged horizontal section on. the line 9-3 of Fig. 4. n

Figure 10 is an enlarged top plan viewof part of the door structure andits bracing and operating means.

natesa part of a building structure having a doorway a and B designates, generally, a canopy door controlling said doorway.

In the present instance the door B is illustrated as comprising Iupper and lower leaves designated as III and II, respectively, and within the purview of the invention these leaves may be of any suitable or desired specic construction. 'I'hey accordingly have not been illustrated in detail, but have been indicated conventionally as of panel form.

'I'he upper leaf I 0 is hinged in any suitable manner, as indicated at I2, at or near its top, to the building structure A at or near the top of the doorway a, for swinging movement between a vertically disposed, closed position and a substantially horizontally disposed, open position in which it extends, canopy-like, forwardly from the building structure at the top of the doorway a. On the other hand, the lower leaf II is mounted in any suitable manner on the upper leaf Ill for vertical sliding movement between raised and lowered positions relative thereo. In this latter connection and as illustrated in the present instance, the upper leaf I Ii includes a vertically disposed I-beam I3 having weldedl or otherwise suitably secured to its web a pair of angle members I4 which, in conjunction with the flanges I5 at the inner side of said I-beam, provide roller trackways. On the other hand, the lower leaf I I includes a pair of vertically disposed channel Amembers I6 which are located at opposite sides of the I-beam I3 andthe flanges II of which constitute roller trackways.

Near the bottom of the upper leaf I0 the I- beam I3 carries rollers I 8 which are disposed in the trackways afforded by the flanges I'I of the channel members I6, while near their tops the channel member I6 carry rollers I 9 which are disposed in the trackways afforded by the angle members I4 and the aforesaid flanges I5 at the inner side of the I-beam I3. Thus, the lower leaf is mounted on the upper leaf for free sliding vertical movement relative thereto.

The upper leaf IIJ is of a height to control approximately the upper half of the doorway a, and the lower leaf II is of a height to control the remaining or lower portion of said doorway. The lower leaf is disposed inwardly relative to the upperv leaf to slide behind said upper leaf, and when said lower leaf is lowered its top is disposed only slightly above the bottom of the upper leaf. Accordingly, the channel members I6 extend suitably above the top of the lower leaf so that when the lower leaf is lowered the rollers I 3 and I9 are 'sufficiently spaced apart to rmly support the lower leaf upon the upper leaf.

Preferably the channel members I6 carry at their outer sides, above the top of the lower leaf II, rollers 20 which, when the lower leaf is fully raised relative to the upper leaf, are disposed to ride behind suitable fixed trackways 2I when the two leaves are swung as a unit to open position, thereby to insure against the lower leaf sliding downwardly relative to the upper leaf during swinging movement of said leaves. 'I'he trackways are curved concentrically with respect to the pivot I2 and may be supported in any desired manner, as for example, upon a pair of plates 22 secured to and depending from a pair of channel members 23 disposed horizontally at or near the top of the doorway a and constituting part of the building structure.

The I-beam I3 extends upwardly considerably above the pivot I2 of the leaf III- and constitutes ,a lever arm for effecting swinging movement of the door as Well as bracing means.

In addition to the lever arm constituted by the upper portion of the I-beam I3, the present door bracing means comprises a pair of arms 24 and 25 which together constitute a brace extending downwardly and inwardly from theupper portion of said I-beam I3 when the door leaves are vertically disposed and act both in compression and tension to positively hold the door against any swinging movement.

The upper arm 24 is pivotally connected at its upper end to the I-beam I3 near the top thereof as indicated at 26, the lower arm 25 is pivotally connected at'its lower end -to a suitable fixed member, as indicated at 21, at a point spaced downwardly and inwardly with respect to the pivot 26 when the upper leaf Ill-is disposed vertically, and the arms 24, 25 are pivotally connected together as indicated at 28. Moreover, any suitable means is provided whereby the arms 24, 25 may swing upwardly and downwardly about their pivots 26 and 21 to and from a position in which they are disposed in or substantially in longitudinal alinement with each other, but cannot .swing below such position. In this connection and as illustrated in the present instance, the means for this purpose may reside in extending the lower end portion of the arm 24 a short distance below the pivot 28 so as to overlap the upper end portion of the arm 25 when said arms are alined, and in providing the lower end-portion of said arm 24 with a suitable stop 29 to engage a top portion of the arm 25 at a point spaced downwardly from'the pivot 28.

The arms 24 and 25 may comprise single mempart of the present doox` bers, but preferably each of said arms is comprised by a pair of members of channel section or other suitable form secured together in parallel, spaced apart relationship as illustrated in the present instance, the members comprising the upper arm 24 being disposed to opposite sides of the I-beam I3 and being more widely spaced apart than the members comprising the lower arm 25 and accommodating the members comprislng the latter arm therebetween.

Carried by the members comprising the upper arm 24 are vertically disposed plates 30 which, at their adjacent or inner sides, are suitably provided with cam channels 3| for cooperation with rollers 32 carried by top portions of the channel members I6 of the lower door leaf.

When the door leaves are disposed vertically and the brace arms 24, 25 are alined in diagonal downward and inward disposition relative to the door, the channels 3| extend diagonally downwardly and inwardly and their lower, open ends are disposed in vertical valinement with the rollers 32, at elevations such that their lower ends will be entered by the rollers 32 when the lower door leaf II ls raised nearly to its fully open position relative to the upper door leaf, but before said lower door leaf has reached its fully raised or open position. Accordingly, when the upper door leaf is in vertically disposed, closed position and is braced in that position by the arms 24, 26, as illustrated in Figs. 1 and 4 of the drawings, the lower door leaf may be raised and lowered to open and close the lower part of the doorway without disturbing the closed, braced status of the upper door leaf, and since the lower leaf cannot swing relative to the upper leaf, both leaves are effectively braced during substantially full opening and closing movements of the lower leaf. When, however, the lower leaf is further raised after its rollers 32 have entered the bottoms of the cam channels 3|, said rollers, due to the downward and inward inclination of said cam channels, cooperate with said cam channels to swing the brace arm 24 upwardly about its pivot 26. This obviously results in the pivot 28 being swung upwardly with consequent upward swinglng of the lower brace arm 25 about its pivot 21, with the result that,`as illustrated in Fig. of the drawings, the pivot 28 is disposedabove a straight line drawn through the pivots 26 and 21 and the arms 24, 25 are disalined and extend in upwardly converging relationship to each other and therefore no longer are effective to hold the door leaves against swinging movement. In fact, since upward swinging movement of the arms 24, 25 about their pivots 26, 21 results in shortening of the distance between said pivots 26, 21, cooperation of the rollers 32 with the channels 3| due to final upward movement of the lower door leaf results not only in releasing the brace to permit the door leaves to swing, but actually initiates swinging movement of said leaves.

Any suitable operating means may be provided for effecting upward movement and controlling downward movement of the lower leaf II I relative to the upper leaf I Il and for effecting swinging movement of said leaves as a unit to canopy-like open position and for controlling their return to vertical position. In this connection and as il-` lustrated in the present instance, a shaft 33, disposed horizontally and extending parallel to the door, is suitably supported, preferably at a point a short distance below the pivot 21 of the brace arm 25 and at a distance inwardly from the pivot I2 of the upper door leaf aboutequal to the length of the lever arm constituted by the portion 0f the I-beam I3 above said pivot, and has fixed thereon a pair of cable drums 34 and 35, the former of which is cylindrical and the latter of which is conical or of other suitable formv larger at one end than at the other.

A pair of cables 36 are fixed at corresponding ends to the drum 34 at opposite ends of said drum, respectively, and extend from said drum upwardly and outwardly over sheaves 31 carried by the I-beam I3 at or near the top thereof and then extend downwardly and inwardly from said sheaves to points adjacent to the drum 34 where they are suitably anchored as indicated t 38. a Inwardly of and adjacent to the door; near the top of the doorway a, is a horizontally disposed power shaft 39 which extends parallel to the door and which has fixed thereon a cable drum 4|I and loose thereon a sheave 4| `while carried by the lower door leaf II`is another sheave 42.

A cable 43 is fixed at one end to the drum 36 at the larger end thereof and extends from said drum substantially horizontally `forwardly over the sheave 4|, then downwardly beneath the sheave 42 and then upwardly to the drum 40 to which it is fixed at its` other end.

When the door leaves are disposed vertically,

the cables 36 vare unwound from the drum 34 and the cable 43 is wound onto the drum 35, extending from the smaller end thereof.

vMore force is required to be exerted through the cable 43 upon the drum 35 to effect rotation` thereof and of the drum 34 towind the cables 36 onto the latter drum and thereby effect swinging movement of the. door leaves by exerting a downward and inward pull on the lever arm con- Y stituted by the upper end portion of the I-beam.-y

lower ends of the cam channels 3|, without disturbing the vertical position of the upper door leaf, especially since lthe upperdoor leaf `is braced against swinging movement by the arms 24 and 25. Accordingly, the lower door leaf may be raised and lowered between its lowermost po sition and a nearly fully raised position to open and close the lower part of the doorway without` disturbing the vertical, braced position of the upper door leaf. enter the lower ends o f the channels 3| further upward movement of the lower leaf is resisted due to the fact any continued upward movement of said leaf must of necessity result in swinging movement of the brace arms in the manner heretofore described and also in initial .opening swinging movement of the door leaves Consequently, continued rotation of the power shaft 39 in a direction to effect winding of the cable 43 thereon, results in unwinding of said cable from the drum 35. This, in turn, results in rotation of the drum 34 and winding of the cables-36 onto the same, with the further result that said cables react from their anchorages 38 and pull the lever arm constituted by the upper portion of the I- beam |3 downwardly. This occurs soon after the rollers 32, by cooperation with the lower portions of the cam channels 3|, effect initial opening swinging movement of the door leaves. 'I'hereafter, the upward swinging movement of the brace arm 24 about `its pivot 26 resulting from continued opening swinging movement of the door leaves exerts through the cam channels 3| and the rollers 32 an upward leverage on the lower door leaf which results in said lower leaf being lifted to fully raised position simultaneouslywith initial opening swinging movement of the door leaves. In this connection it will be observed that the rollers 20 are positioned on the lower door so that they pass overthe tops of the trackways 2| with initial opening swinging movement of the door leaves and begin to travel behind said trackways as such movement of said door leaves continues, thereby serving positively to` When, however, the rollers 32 it approaches the larger end of said drum with the result that progressively increasing leverage is exerted on the shaft 33 to rotate the same to effect ,opening swinging movement of the door leaves as said leaves approach substantially horizontal position and require more power to effect their opening swinging movement.

As the door leaves continue to swing toward open position the brace arm 24 swings upwardly about its pivot 26 and the brace arm 25 swings upwardly and rearwardly about its pivot 21 until the pivots I2, 26 and 28 become disposed in a straight line with the brace arm 24 extending upwardly from the I-beam I3. Thereafter, the brace arm 24 swings forwardly and downwardly relative to the I-beam I3 and the brace arm 25 swings forwardly and downwardly until said brace arms reach the relationship shown in Fig. 6 of the drawings when the door reaches its fully open, canopy-like position. During these swinging movements the rollers 32 travel through the cam channels 3| and leave the open, upper ends of said channels, but upon closing of the door they again enter Ithe open, upper ends of said channels and travel downwardly therethrough. In other words, when the door is closed, which is effected by gravity under the control of the power shaft 39, the various parts partake of the reverse of their described door opening movements, In this connection it will be noted that the upperv portions of the cam channels 3| are curved in accordance with the swinging movements partaken of by said cam channels during opening and closing swinging movements of the door so that the lower leaf is raised just to and not beyond its fully raised position relative to thel upper leaf and is not oscillated vertically as the door is swung to open position.

Preferably, but not necessarily, a second cable 44 is attached at one end to the drum 40 and extends from said drum over a suitable sheave or sheaves 45 to any suitable point where it is equipped at its other end with a weight 46. Thus, the lower leaf may be effectively counterweighted. The two cables 43 and 44 may be attached to opposite ends of the drum 40 so that as one of them winds onto lsaid drum the other unwinds therefrom.

While the shaft 33 may be supported in any suitable manner, one practical manner of supporting the same is in bearings carried by a suitable framework 41 depending from the channel members 23, which framework may also be utilized as an anchorage for the cables 36. Moreover, the fixed members to which the lower ends of the brace arms 25 are pivoted may also be carried by thechannel members 23.

Of course, only one or as many as desired of the described braces and associated operating means, whether of the form illustrated and described or of any other suitable form, may be employed in connection with any given door or door section. In any event, it will be apparent that the bracing means serves effectively to hold the door leaves against swinging movement except when the lower door leaf is substantially fully raised relative to the upper door leaf, and that, even then, so long as the rollers 32 remain in the channels 3| only predetermined opening or closing swinging movements of the door can occur. Moreover, it is further apparent that the present bracing and operating means are disposed quite high so that they do not interfere with utilization of the space behind and y adjacent to .the door for substantially the full height thereof for storage or other purposes.

Without further description it is thought that the features and advantages of .the invention will be readily apparent to those skilled in the art, and it will of course be understood that changes in the form, proportion and minor details of construction may be resorted to, without departingr from the spirit of the invention and scope of the appended claims.

Iclaim:

l. A door comprising an upper leaf pivoted fori swinging movement between vertical and substantially horizontal closed and open positions, respectively, a lower leaf mounted on said upper leaf for vertical sliding movement between raised and lowered, open and closed positions, respectively, relative thereto, a brace for the upper leaf comprising a lever arm extending from said upper leaf above the pivot thereof, an upper brace arm pivoted at its upper end to said lever arm a-t a point above the pivot of said upper leaf, a lower brace arm having a ,fixed pivot at a point spaced inwardly from the pivot of said upper leaf and at' a point spaced downwardly from the pivotal connection of said upper brace arm with saidlever arm when the said upper leaf is disposed vertically, a pivotal connection between said brace arms, means to insure a substantially alined relationship of said brace arms in which Ithey extend diagonally downwardly and inwardly from said lever arm when the upper door leaf is disposed vertically and thereby hold said upper leaf against swinging movement, a pair of elements one on the upper brace arm and the other on the lower leaf acting one upon the other in response to the final portion of raising movement of the lower leaf relative to the upper leaf to urge said upper brace arm upwardly about its pivotal connection with said lever arm, thereby to disaline said brace arms and to initiate opening swinging movement of the door leaves and to permit continued opening swinging movement of said leaves, and means for raising said lower leaf relative to said upper leaf and for thereafter swinging said leaves to open position.

2. A door comprising an upper leaf pivoted for swinging movement between vertical and substantially horizontal closed and open positions, respectively, a lower leaf mounted on said upper leaf for vertical sliding movement between raised and lowered, open and closed positions, respectively, relative thereto, a brace for the upper leaf comprising a leverl arm extending from said upper leaf above the pivot thereof, an upper brace arm pivoted at its upper end to said lever arm at a point above the pivot of said upper leaf, a lower brace arm having a xed pivot at a point spaced inwardly from 'the pivot of said upper leaf and at a point spaced downwardly from the pivotal connection of said upper brace arm with said lever arm when the said upper leaf is disposed vertically, a pivotal connection between said brace arms, means -to insure a substantially alined relationship of said brace arms in which they extend diagonally downwardly and inwardly from said lever arm when the upper door leaf is disposed vertically and thereby hold said upper leaf against swinging movement, cam and roller means one on the upper brace arm and the other on the lower door leaf cooperating in response to the final portion -of raising movement of the lower leaf relative to the upper leaf :to swing said upper brace arm upwardly about its pivotal connection with said lever arm, thereby to disaline said brace arms and to initiate opening swinging movement of the door leaves and to permit continued opening swinging movement of said leaves, and means for raising said lower leaf relative to said upper leaf and for thereafter swinging said leaves to open position.

3. A door comprising an upper leaf pivoted for swinging movement between vertical and substantially horizontal closed and open positions, respectively, a lower leaf mounted'on said upper leaf for vertical sliding movement between raised and lowered, open and closed positions, respectively, relative thereto, a brace for the upper leaf comprising a leve'x arm extending from said upper leaf above the pivot thereof, an upper brace arm pivoted at its upper end -to said lever arm at a point above the pivot of said upper leaf, a lower brace arm having a fixed pivot at a point spaced inwardly from the pivot of said upper leaf and at a point spaced downwardly from the pivotal connection of said upper brace arm with said lever arm when the said-upper leaf is disposed vertically, a pivotal connection between said brace arms, means to insure a substantially alined relationship of said brace arms in which they extend diagonally downwardly and inwardly from saidlever arm when the upper door leaf is disposed vertically and thereby hold said upper leaf against swinging movement, cam means carried by the upper brace arm and inclined upwardly and outwardly when the upper door leaf is disposed vertically, means on the lower leaf for cooperation with said `cam means in response to the final portion of raising movement of the lower leaf relative to the upper leaf to swing said upper brace arm upwardly about its pivotal connection with said lever arm, -thereby to disaline said brace arms and to initiate opening swinging movement of the door leaves and to-permit con- Itlnued opening swinging movement of said leaves,v

and means for raising said lower leaf relative to said upper leaf and for thereafter swinging said leaves to open position;

4. A door comprising an upper leaf pivoted for swinging movement between vertical and substantially horizontal closed and open positions, respectively, a'lower leaf mounted on said upper leaf for vertical sliding movement between raised and lowered, open and closed positions. respectively, relative thereto, a brace for the upper leaf comprising a lever arm extending from said upper leaf above the pivot thereof, an upper brace arm pivotedfat its upper end to said-'lever arm at a point above the pivot of said upper leaf, a lower brace arm having a xed pivot atL a point spaced inwardly fromA the pivot of said upper leaf and at a point spaced downwardly,

from the pivotal connection of saidupper brace arm with said lever arm when the said upper leaf is disposed vertically a pivotal connection between said brace arms, means to insure a substantially alined relationship of said brace arms in which they extend diagonally 'downwardly and inwardly from said lever arm when the upper door leaf isdisposed vertically and thereby hold said upper leaf against swingingmovement, a

plate carried by said upperbrace arm, means carried by said plate defining a cam channelv which is inclined upwardly and outwardly when the upper leaf is disposed vertically, a roller on -the lower leaf to enter said cam channel and to of the door leaves and to permit continued open-` ing swinging movement of said leaves, and means for raising said lower leaf relative to said upper leaf and for thereafter swinging said leaves to open position.

5. 'I'he combinationas set forth in claim 1 in which the fixed pivot ofthe lower brace arm is disposed above the pivot of the upper leaf, whereby the entire bracing means is disposed above the pivot of said upper leaf.

6. The combination as set forthin claim 1 in which the bracing arms each comprise a pair of members disposed in side to side spaced apart relationship.

7. A door comprising an upper leaf pivoted for swinging movement between vertical and substantially horizontal closed and open positions, respectively,'a lower leaf mounted on said upper leaf. for vertical sliding movement between raised and lowered, open and closedl positions, respectively, relative thereto,`brace means cooperating with the upper leaf to hold the same against swinging movement when said leaf is disposed vertically, cam and cam follower means one on said-brace means and the other on said lower door leaf acting one upon the other in response to the final portion of raisingmovement of the lower leaf relative to the upper leaf to exert force on said bracing means to release the same, there- `by to permit the two leaves to be swung as a unit to open position, and means for raising said lower Y leaf relative to said upper leaf and for thereafter swinging said leaves as' a unit to open position.

8. A door comprising an upper leaf pivoted for swinging' movement between vertical and substantially horizontal closed and open positions, respectively. a lower leaf mounted on said upper leaf for vertical sliding movement between raised and lowered, open and closed positions, respectively, relative thereto, brace means cooperating with the upper leaf -to hold the same against swinging movement when said leaf is disposed vertically, a pair of elements one on said brace means and the other on said lower leaf acting one upon'the other in response to the final portion of raising movement of the lower leaf relative to 4the upper leaf to exert force on said brace means to release same and to initiate swinging movement of theleaves as a unit toward open position, and means for raising said lower leaf relative to said upper leafand for thereafter swinging said leaves as a unit to open position.

DAVID H. MORGAN. 

